This invention relates to locking and sealing assemblies, and more particularly to means for sealing the interior of a linear motion potentiometer (LMP) body which is enclosed by a casing during operation but must be accessible from the outside at other times.
It is often necessary to seal instrument assemblies against harmful operating environments and yet have convenient access to the instrument when desired for cleaning and maintenance. For example, in order to measure the cross section of an oil well at various levels a number of LMP's may be dropped to the lowest level of the well and then drawn up toward the surface. An operating rod emanating from each LMP maintains contact with the side of the well and is pushed into or out from the potentiometer according to the measured well dimension at each level. The LMP's are normally enclosed in a protective casing, but must be periodically opened for removal of any oil which may have entered and dirtied the instrument elements.
There are thus two factors in the construction of such devices that have conflicted to a certain extent in the past: the need for a good environmental seal to protect the interior mechanism, and the ability for the device to be readily disassembled for servicing and cleaning and then reassembled. A common technique has been to provide O-rings around each end of the instrument body which are compressed by the casing as it is slid over the body, thereby forming a secure seal. To secure the casing to the body it has been necessary to use auxiliary devices such as screws or locking rings. While a satisfactory seal can be obtained in this manner, the disassembly and reassembly procedures necessary to remove the casing from the body for servicing the instrument and then repositioning the casing are somewhat cumbersome and subject to improvement in terms of both the complexity of the apparatus and the time required for each operation.